AmazonBasics Air Stability Cushion with Pump Stability cushion helps improve balance, coordination, and flexibilitygreat for active sitting/standing and core strengthening Large spiky dimples on one side for standing on; small dimples on reverse side for sitting on Durable construction made from PVC Includes small needle hand pump for easily inflating the cushion to desired level of firmness Measures 14 inches (35 cm) in diameter